Other than forced-induction or NOS, what are the *big* performance mods that can be done to a 2.5L......if there is any?

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1984 2M4 SE Auto *stock*
1997 Covette 6-speed *slighty modified* ;)
My main squeeze!

I've been playing with the 4bangers more than anything in Fieros and have come up to the belief that the only serious HP gains to be made in a Tech or through rebuilding it using performance parts and also boring it, port and polish but dont polish too much. also, tech 4's love back pressure so DON'T put a free flow exhaust on it.

ok, my 2 cents anyways. And welcome to the Forum.

PS) Have you checked out the Texas Get Together post in General yet?

I've been toying with the idea of getting a 2m4 w/manual and trying to squeeze some power out of the Duke with a performance rebuild. I've heard the biggest weaknesses are the bottom end,the connecting rods,and the valvetrain(redline). Could this all be cured with a forged crank,SBC connecting rods/pistons,different cam,and valve springs/roller rockers? I'm sure some valve porting and a higher compression would help too.

hmm well this might help someone.

Performance rebuild kits are ok but check what parts are included.

List of my planned parts:
Comp cam 1200-5200rpm cam (Just realized this was wrong )
Lunati roller rockers 1.7
specialty 5.9" connecting rods
.030 over bore hyperuetic pistons
chrome molly rings
Custom head work to open up the oil flow
high flow oil pump
custom machined SD crank (machinist resized it to fit the block and rebalanced it)
Billet timing gear assempbly (from a friend)
Custom made intake manifold with 4 barrel carburator setup.
hooker header

thats about it for now. Still having problems aquiring certain parts. Estimated HP if the math was accurate is around 190-215hp. Never done that myself so don't know how high it will go.

[This message has been edited by RedHaze86SD4 (edited 01-30-2002).]

I currenly have the motor pulled (and completely torn apart) and i'm just trying to figure out the best thing to do......rebuild engine to stock or a perfomance rebulid(if that's possible).

Is there any shop or vendor that sells a "performance package" that i could use in my rebuild process? Or will i have to special order every thing like the cam, crank, rods, pistons, etc.?

You'll probably have to search for everything seperately. Haze, are you going to do anything to the head gasket,maybe o-ring the block or copper? When the compression starts to rise the stock gasket will probably fail.

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85 GT Turbo intercooled

Someone suggested I goto a company (sorry but I wont name the company) to get graphite coated coppergaskets. Having never heard of these I thought that'd be kool and the descriptions sounded great, but the POS company kept screwing me. so we wont go there

Right now I'm trying to find better gaskets. Chrome Molly rings are great for pistons, too bad ya cant get similar for everything else. Might try to use a SD gasket from GM and modify it a little. Someone suggested gasket coating the OEM style gaskets insert? but there again is something I'm not familiar with.

Word of advice, if you have the head off the block and can get it cleaned profesionally after modifying it, or can get someone to do everything for you. Go to a junkyard and look at the head from a 91 grand am. probably any similar year of U code tech will be the same. Around the lifter rods theres a little bit of Iron but theres alot thats removed for better oil flow. I'm having my heads reworked to match or semi match that design. Makes head weigh less plus enables for better cooling. just dont get too carried away with it.

also, I don't recommend going over .040 on a bore. .030 should be fine. If you go with 5.7" connecting rods I THINK (check before trying this though) you can run domed pistons. flat pistons will work with 6" since I think thats stock height. you can run specialty 6.1" or 6.2" if you use reverse domed pistons or recessed, butyou have to be carefull with those because theyre not as strong, also your more likely to tap a valve. Was talking to a race mechanic and he said try polishing out the intake valves and maybe enlargening them by up to .008 for better flow, but don't do anything except maybe polish the exhaust. Have never tried this but it might be possible.

Another thing I found out. You CAN use the turbo assembly from either the Thunderquack or the grand am 2L turbo. either applications needs minor modification if you know what to do. And no I don't otherwise I would have already.

If you run Nitros or turno on a duke modified the way i want to, you shouldnt see the problems you would if you do it to an OEM setup. the Hyperuetice pistons and the chrome Molly rings both love higher RPMs and can handle more pressure in the chamber. But still be carefull.